Benzene contains only carbon and hydrogen and has a molar mass of 78.1 g/mol.?

Question

Analysis shows the compound to be 7.74% H by mass. Find the empirical and molecular formulas of benzene. Can anybody help me on this one?

Answer 1

Assume you have a 100-g sample. Convert the grams of H and C to moles. Then, find the molar ratio of C and H.

If there are 7.74 g H, then there must be 100. - 7.74 = 92.26 g C

7.74 g H x (1 mol / 1.008 g) = 7.68 mol H

92.26 g C x (1 mol / 12.011 g) = 7.68 mol C

mol C / mol H = 7.68 / 7.68 = 1.00

The empirical formula is CH.

Answer 2

C6H6